734 



SCIENCE 



[N. S. Vol. XXXII. No. 830 



heteroclitiis : the optic vesicles, instead of 

 being formed as a widely separated pair, 

 were caused to approach the median line, 

 and in about 50 per cent, of the embryos 

 experimented upon the changes were so 

 profound as to give rise to cyclop ean mon- 

 sters. Many other instances might be cited 

 of definite effects of physical and chemical 

 agencies on particular organs, and we are 

 now forced to admit that inherited ten- 

 dencies may be completely overcome by a 

 minimal change in the environment. The 

 nature of the organism, therefore, is not 

 all important, since it yields readily to in- 

 fluences which at one time we should have 

 thought inadequate to produce perceptible 

 changes in it. 



It is open to any one to argue that, in- 

 teresting as experiments of this Mnd may 

 be, they throw no light on the origin of 

 permanent — that is to say, inheritable — 

 modifications of structure. It has for a 

 long time been a matter of common knowl- 

 edge that individual plants and animals 

 react to their environment, but the modi- 

 fications induced by these reactions are 

 somatic; the germ-plasm is not affected, 

 therefore the changes are not inherited, 

 and no permanent effect is produced in the 

 characters of the race or species. It is 

 true that no evidence has yet been pro- 

 duced to show that form-changes as pro- 

 found as those that I have mentioned are 

 transmitted to the offspring. So far the 

 experimenters have not been able to rear 

 the modified organisms beyond the larval 

 stages, and so there are no offspring to 

 show whether cyclopean eyes or modified 

 forms of spicules are inherited or not. In- 

 deed, it is possible that the balance of 

 organization of animals thus modified has 

 been upset to such an extent that they are 

 incapable of growing into adults and re- 

 producing their kind. 



But evidence is beginning to accumulate 



which shows that external conditions may 

 produce changes in the germ-cells as well 

 as in the soma, and that such changes may 

 be specific and of the same kind as simi- 

 larly produced somatic changes. Further, 

 there is evidence that such germinal 

 changes are inherited — and, indeed, we 

 should expect them to be, because they are 

 germinal. 



The evidence on this subject is as yet 

 meager, but it is of good quality and comes 

 from more than one source. 



There are the well-known experiments of 

 Weismann, Standfuss, Merrifield and E. 

 Fischer on the modification of the color 

 patterns on the wings of various lepi- 

 doptera. 



In the more northern forms of the fire- 

 butterfiy, Clu-ysophanus (Polyommatus) 

 phlcBas, the upper surfaces of the wings are 

 of a bright red-gold or copper color with a 

 narrow black margin, but in southern 

 Europe the black tends to extend over the 

 whole surface of the wing and may nearly 

 obliterate the red-gold color. By exposing 

 pupee of caterpillars collected at Naples to 

 a temperature of 10° G. Weismann ob- 

 tained butterflies more golden than the 

 Neapolitan, but blacker than the ordinary 

 German race, and conversely, by exposing 

 pupte of the German variety to a tempera- 

 ture of about 38° C, butterflies were ob- 

 tained blacker than the German, but not 

 so black as the Neapolitan variety. Simi- 

 lar deviations from the normal standard 

 have been obtained by like means in vari- 

 ous species of Vanessa by Standfuss and 

 Merrifield. Standfuss, working with the 

 small tortoise-shell butterfly {Vanessa 

 urticce) , produced color aberrations by sub- 

 jecting the pupffi to cold, and found that 

 some specimens reared under normal con- 

 ditions from the eggs produced by the 

 aberrant forms exhibited the same aber- 

 rations, but in a lesser degree. Weis- 



